(1) Field of the Invention
The present invention relates to a method of manufacturing a glue-coated element, to the glue-coated element, an adhesive compound, and to a method of producing glue-coated derived-timber panels, and to panels produced with this method.
(2) Prior Art
Adhesives and the corresponding adhesive compounds can be classified into four categories. First, adhesives which are applied wet, i.e. in an aqueous medium or solved in a solvent, to the element(s) to be glued. The elements to be bonded are glue-coated, joined and fixed with the aid of auxiliary means, for example, by cramps or clamps in the predetermined position during the period of time which the glue takes to set by the removal of water or solvent or by a chemical reaction, and the glue bond is established. It usually takes a few hours for the glue to set. The application of the glue is carried out immediately before joining the elements.
Second, adhesives are known which consist of two components interacting with one another. A first component is applied to the element(s) to be joined, and dried as necessary, so that an adhesive film is formed. This adhesive film is then activated by adding the second component, such as by adding small amounts of water. The second component can be applied either immediately before processing, or it can be a component part of the adhesive film, for example in the form of micro capsules, but spatially separated from the first component. Typical examples of these technologies are described in WO 01/94721; WO 02/063114 and DE 102 12 324.
Third, adhesives are known which are applied as a film to the elements to be bonded and which are then softened without the addition of further components, but by the prolonged exposure to high temperatures and/or pressures, and which set again when cooled down and thus form a bond between the elements. These are adhesives which are usually industrially used, since their processing conditions with respect to the temperature and pressure are to be precisely adhered to. These adhesives are processed in the factory, up to the point where the adhesive has completely set.
Fourth, adhesives are known which have a sticky surface in a dry condition and which form a bond when a contact is established without the application of high pressures. Since the adhesive force of these adhesives is weak, the adhesive bonds are usually separable. In GB 2 377 457, such an pressure-sensitive adhesive is suggested for bonding two panels. The film, formed by one pressure-sensitive adhesive is soft and permanently sticky, however, which means that it loses its function, for example, when dust settles on it. The weak cohesive forces which a pressure-sensitive adhesive film develops, cause the elements bonded by means of a pressure-sensitive adhesive to easily come apart, even when they are only slightly stressed. The minimal adhesive force and the inevitable clogging of the adhesive film brought about by simple dust, make it unsuitable for industrial use, where the adhesive bond has to have at least a minimum strength.
Summarizing, it can be said that adhesives which have to establish a permanent bond are applied either immediately in connection with the joining of the bond or need the addition of a second component or the application of high pressures and/or temperatures. An adhesive which can be applied to the elements to be glued together and which results in a strong, durable bond at a period of time remote from the application and without the addition of a second component or the application of high pressures and/or temperatures is not known.